Mediating Coupling of Quantum Bits Using Chains of Resonators and Tunable Inductive Couplers

This disclosure relates generally to superconducting quantum computing systems and, in particular, techniques for mediating interactions between quantum bits using coupling buses. A quantum computing system can be implemented using superconducting circuit quantum electrodynamics (cQED) architectures that are constructed using quantum circuit components such as, e.g., superconducting quantum bits and other types of superconducting quantum devices that are controlled using microwave and/or flux bias control signals. In general, superconducting quantum bits (qubits) are electronic circuits which are implemented using components such as superconducting tunnel junctions (e.g., Josephson junctions), superconducting quantum interference devices (SQUIDs), inductors, and/or capacitors, etc., and which behave as quantum mechanical anharmonic (non-linear) oscillators with quantized states, when cooled to cryogenic temperatures. A qubit can be effectively operated as a two-level system in a computational subspace comprising a ground state |0and a first excited state |1of the qubit, due to the anharmonicity imparted by a non-linear inductor element (e.g., Josephson junction inductance) of the qubit, which allows the ground and the first excited states to be uniquely addressed at a transition frequency of the qubit, without significantly disturbing higher excited states of the qubit (e.g., |2, |3etc.).

Various types of quantum information processing algorithms can be implemented using a superconducting quantum processor which comprises multiple superconducting qubits which can be coherently controlled, placed into quantum superposition states, exhibit quantum interference effects, and become entangled with one another, by applying various types of quantum gate operations (e.g., single-qubit gate operations, two-qubit gate operations, etc.) to the superconducting qubits. As quantum processors are scaled with increasing numbers of superconducting qubits and higher integration densities, a primary challenge is being able to scale up the number of qubits without introducing additional channels of noise and unwanted exchange interactions between qubits which can result in correlated gate errors. For example, with increasing numbers of qubits on a given quantum chip, the ability to implement long-range interactions (e.g., several millimeters) between pairs of qubits on the quantum chip becomes increasingly problematic to achieve high on/off ratios of qubit-qubit exchange couplings, and to prevent unwanted interactions with spectator qubits, which are desired to ensure high-speed and high-fidelity gate operations.

Exemplary embodiments of the disclosure include techniques for mediating interactions (e.g., long range interactions) between quantum bits to facilitate quantum computing operations such as two-qubit gate operations.

An exemplary embodiment includes a device which comprises a first quantum bit, a second quantum bit, and a coupling bus connecting the first quantum bit and the second quantum bit. The coupling bus comprises a plurality of transmission line resonators which are coupled in series, and at least one tunable inductive coupler to control a coupling between a first transmission line resonator and a second transmission line resonator of the plurality of transmission line resonators.

Another exemplary embodiment includes a system which comprises a quantum processor and a control system. The quantum processor comprises a first quantum bit, a second quantum bit, and a coupling bus connecting the first quantum bit and the second quantum bit. The coupling bus comprises a plurality of transmission line resonators which are coupled in series, and at least one tunable inductive coupler to control a coupling between a first transmission line resonator and a second transmission line resonator of the plurality of transmission line resonators. The control system is configured to generate a control signal to tune the at least one tunable inductive coupler of the coupling bus into one of: a first operating state to couple the first transmission line resonator and the second transmission line resonator to enable exchange coupling between the first quantum bit and the second quantum bit over the coupling bus; and a second operating state to decouple the first transmission line resonator and the second transmission line resonator to suppress exchange coupling between the first quantum bit and the second quantum bit over the coupling bus.

Another exemplary embodiment comprises a method which comprises controlling an exchange interaction between a first quantum bit and a second quantum bit that are connected by a coupling bus which comprises a plurality of transmission line resonators that are coupled in series, and at least one tunable inductive coupler to control a coupling between a first transmission line resonator and a second transmission line resonator of the plurality of transmission line resonators, wherein controlling the exchange interaction between the first quantum bit and the second quantum bit comprises: tuning the at least one tunable inductive coupler of the coupling bus into a first operating state to couple the first transmission line resonator and the second transmission line resonator to enable exchange coupling between the first quantum bit and the second quantum bit over the coupling bus; and tuning the at least one tunable inductive coupler of the coupling bus into a second operating state to decouple the first transmission line resonator and the second transmission line resonator to suppress exchange coupling between the first quantum bit and the second quantum bit over the coupling bus.

Other embodiments will be described in the following detailed description of exemplary embodiments, which is to be read in conjunction with the accompanying figures.

Exemplary embodiments of the disclosure will now be described in further detail with regard to techniques for mediating interactions (e.g., long range interactions) between quantum bits to facilitate quantum computing operations such as two-qubit gate operations.

An exemplary embodiment includes a device which comprises a first quantum bit, a second quantum bit, and a coupling bus connecting the first quantum bit and the second quantum bit. The coupling bus comprises a plurality of transmission line resonators which are coupled in series, and at least one tunable inductive coupler to control a coupling between a first transmission line resonator and a second transmission line resonator of the plurality of transmission line resonators.

Advantageously, the exemplary coupling bus architectures as discussed herein enable long-range, highly tunable control of exchange interactions between qubits. The exemplary coupling bus architectures are designed to eliminate low-frequency modes that are normally present in long-range buses, and provide fast and high ON/OFF ratios of qubit-qubit exchange interactions by virtue of separating a coupling bus into multiple segments of transmission line resonators, and utilizing flux-tunable inductive couplers to dynamically control the inductive coupling of the transmission line resonators, or utilizing a combination of flux-tunable inductive couplers and fixed interactions using fixed coupling capacitor or coupling inductors, to couple the multiple segments of transmission line resonators.

In another exemplary embodiment, which may be combined with one or more of the embodiments of the preceding paragraphs, the at least one tunable inductive coupler is configured to be tuned into one of: a first operating state to couple the first transmission line resonator and the second transmission line resonator to enable exchange coupling between the first quantum bit and the second quantum bit over the coupling bus; and a second operating state to decouple the first transmission line resonator and the second transmission line resonator to suppress exchange coupling between the first quantum bit and the second quantum bit over the coupling bus.

Another exemplary embodiment includes a system which comprises a quantum processor and a control system. The quantum processor comprises a first quantum bit, a second quantum bit, and a coupling bus connecting the first quantum bit and the second quantum bit. The coupling bus comprises a plurality of transmission line resonators which are coupled in series, and at least one tunable inductive coupler to control a coupling between a first transmission line resonator and a second transmission line resonator of the plurality of transmission line resonators. The control system is configured to generate a control signal to tune the at least one tunable inductive coupler of the coupling bus into one of: a first operating state to couple the first transmission line resonator and the second transmission line resonator to enable exchange coupling between the first quantum bit and the second quantum bit over the coupling bus; and a second operating state to decouple the first transmission line resonator and the second transmission line resonator to suppress exchange coupling between the first quantum bit and the second quantum bit over the coupling bus.

Another exemplary embodiment comprises a method which comprises controlling an exchange interaction between a first quantum bit and a second quantum bit that are connected by a coupling bus which comprises a plurality of transmission line resonators that are coupled in series, and at least one tunable inductive coupler to control a coupling between a first transmission line resonator and a second transmission line resonator of the plurality of transmission line resonators, where controlling the exchange interaction between the first quantum bit and the second quantum bit comprises: tuning the at least one tunable inductive coupler of the coupling bus into a first operating state to couple the first transmission line resonator and the second transmission line resonator to enable exchange coupling between the first quantum bit and the second quantum bit over the coupling bus; and tuning the at least one tunable inductive coupler of the coupling bus into a second operating state to decouple the first transmission line resonator and the second transmission line resonator to suppress exchange coupling between the first quantum bit and the second quantum bit over the coupling bus.

In another exemplary embodiment, which may be combined with one or more of the embodiments of the preceding paragraphs, tuning the at least one tunable inductive coupler of the coupling bus into the first operating state to couple the first transmission line resonator and the second transmission line resonator to enable exchange coupling between the first quantum bit and the second quantum bit over the coupling bus, comprises generating control signal to flux-bias the at least one tunable inductive coupler of the coupling bus into the first operating state to inductively couple the first transmission line resonator and the second transmission line resonator and cause mode hybridization of frequency modes of the first transmission line resonator and the second transmission line resonator to generate a hybridized frequency mode which moves towards respective transition frequencies of the first quantum bit and the second quantum bit.

In another exemplary embodiment, which may be combined with one or more of the embodiments of the preceding paragraphs, the first transmission line resonator and the second transmission line resonator are nominally identical and have a resonant frequency that is greater than the transition frequencies of the first quantum bit and the second quantum bit, wherein the hybridized frequency mode has a frequency that is less than the resonant frequency of the at least two transmission line resonators.

In another exemplary embodiment, which may be combined with one or more of the embodiments of the preceding paragraphs, the plurality of transmission line resonators comprise nominally identical coplanar waveguide resonators.

In another exemplary embodiment, which may be combined with one or more of the embodiments of the preceding paragraphs, the at least one tunable inductive coupler comprises a superconducting loop comprising at least one Josephson junction.

In another exemplary embodiment, which may be combined with one or more of the embodiments of the preceding paragraphs, the at least one tunable inductive coupler comprises a radio frequency superconducting quantum interference device.

In another exemplary embodiment, which may be combined with one or more of the embodiments of the preceding paragraphs, the at least one tunable inductive coupler comprises a direct current superconducting quantum interference device.

In another exemplary embodiment, which may be combined with one or more of the embodiments of the preceding paragraphs, the coupling bus further comprises at least one fixed coupling device to provide a fixed coupling between the second transmission line resonator and a third transmission line resonator of the plurality of transmission line resonators.

In another exemplary embodiment, which may be combined with one or more of the embodiments of the preceding paragraphs, the fixed coupling device comprises one of a coupling capacitor and a coupling inductor.

It is to be understood that the various features shown in the accompanying drawings are schematic illustrations that are not drawn to scale. Moreover, the same or similar reference numbers are used throughout the drawings to denote the same or similar features, elements, or structures, and thus, a detailed explanation of the same or similar features, elements, or structures will not be repeated for each of the drawings. Further, the term “exemplary” as used herein means “serving as an example, instance, or illustration.” Any embodiment or design described herein as “exemplary” is not to be construed as preferred or advantageous over other embodiments or designs.

Further, it is to be understood that the phrase “configured to” as used in conjunction with a circuit, structure, element, component, or the like, performing one or more functions or otherwise providing some functionality, is intended to encompass embodiments wherein the circuit, structure, element, component, or the like, is implemented in hardware, software, and/or combinations thereof, and in implementations that comprise hardware, wherein the hardware may comprise quantum circuit elements (e.g., quantum bits, coupling buses, tunable inductive couplers, control circuitry, etc.), discrete circuit elements (e.g., transistors, inverters, etc.), programmable elements (e.g., application specific integrated circuit (ASIC) chips, field-programmable gate array (FPGA) chips, etc.), processing devices (e.g., central processing units (CPUs), graphics processing units (GPUs), etc.), one or more integrated circuits, and/or combinations thereof. Thus, by way of example only, when a circuit, structure, element, component, etc., is defined to be configured to provide a specific functionality, it is intended to cover, but not be limited to, embodiments where the circuit, structure, element, component, etc., is comprised of elements, processing devices, and/or integrated circuits that enable it to perform the specific functionality when in an operational state (e.g., connected or otherwise deployed in a system, powered on, receiving an input, and/or producing an output), as well as cover embodiments when the circuit, structure, element, component, etc., is in a non-operational state (e.g., not connected nor otherwise deployed in a system, not powered on, not receiving an input, and/or not producing an output) or in a partial operational state.

In addition, the term “quantum chip” or “qubit chip” as used herein refers to a die (e.g., semiconductor die) which comprises a superconducting electronic integrated circuit comprising various superconducting components such as qubits, tunable couplers, ground planes, signal coplanar waveguides, and resonators, etc. A plurality of dies having the same and/or different configurations of superconducting electronic integrated circuits, can be fabricated on a wafter (e.g., semiconductor wafer), wherein the individual dies can be diced (cut) from the wafer using a die singulation process to provide singulated dies which can be packaged together to construct a modular quantum processor architecture. The terms “quantum chip” and “qubit chip” and “die” are synonymous terms and used interchangeably herein.

For large-scale quantum computation, a quantum processor comprising an array of superconducting qubits can utilize couplers to mediate intra-chip qubit-qubit interactions to, e.g., enable high-fidelity two-qubit gate operations (e.g., entanglement operations). For example, coplanar waveguide (CPW) transmission line resonators (or CPW resonators) can be utilized to enable long-range interactions (i.e. several millimeters) between two qubits disposed on a given quantum chip. However, utilizing CPW resonators to implement long-range coupling between qubits can be problematic for various reasons. For example, when utilizing CPW resonators for long-range qubit-qubit coupling, it is difficult to achieve high ON/OFF ratios for qubit-qubit exchange interactions. Indeed, the ability to quicky turn ON and turn OFF the exchange interaction between two qubits is needed to achieve high-speed and high-fidelity two-qubit gate operations. Moreover, utilizing a CPW resonator alone to implement long-range qubit-qubit coupling makes it difficult to control unwanted interactions with spectator qubits.

In addition, when utilizing relatively long CPW resonators for qubit-qubit coupling, such CPW resonators can possess multiple low-frequency (<4 GHz) modes, which may couple to the qubits. Such low-frequency modes are undesirable as they could possess excess thermal population of their excited states, which can potentially cause dephasing of the qubits due to the longitudinal coupling between the qubits and the low frequency modes. In this regard, the transition frequencies of the qubits can shift in response to the state of the population of the low frequency modes, leading to gate errors.

To address the above-noted disadvantages associated with long-range qubit-qubit coupling, exemplary embodiments of the disclosure provide coupling buses and coupling techniques to mediate long-range interactions between qubits, while suppressing the formation of low-frequency modes within long-range coupling buses, and robustly suppressing spectator effects in a superconducting quantum computer. As explained in detail below, the exemplary long-range qubit-qubit coupling buses and techniques as described herein are designed to eliminate unwanted low-frequency modes that can arise in long-range buses, and provide high ON/OFF ratio of long-range interactions between qubits by implementing a coupling buses which comprise multiple transmission line resonators that are coupled together using flux-tunable inductive couplers, or a combination of flux-tunable inductive couplers and fixed coupling device (coupling capacitors and/or coupling inductors).

1 FIG. 1 FIG. 100 102 102 110 120 130 110 120 130 110 120 130 110 120 110 120 For example,schematically illustrates a device which comprises a coupling bus that is configured to mediate interactions between quantum bits, according to an exemplary embodiment of the disclosure. In particular,schematically illustrates a devicewhich comprises a quantum chipand various quantum components disposed on the quantum chip, where such quantum components include, but are not limited to, a first qubit, a second qubit, and a coupling busthat is coupled to the first and second qubitsand. In some embodiments, the coupling buscomprises a chain of transmission line resonators and one or more tunable inductive couplers (e.g., flux-tunable inductive couplers) that are configured to provide tunable inductive coupling between adjacent transmission line resonators. The first qubitand the second qubitcan be any type of qubit including, but not limited to, superconducting transmon qubits, superconducting fluxonium qubits, superconducting multimode qubits (e.g., superconducting tunable coupler qubits (TCQs)), spin qubits, or other types of qubits that can be capacitively coupled to a transmission line resonator of the coupling bus, etc. In some embodiments, the first qubitand the second qubitcomprise fixed-frequency qubits (not tunable). In other embodiments, the first qubitand the second qubitcomprise flux-tunable qubits with tunable transition frequencies.

102 112 122 114 124 132 130 110 120 112 122 110 120 112 122 110 120 The quantum chipfurther comprises a plurality of control lines including, but not limited to, qubit drive linesand, qubit readout resonatorsand, and one or more flux bias control linesthat are configured to apply one or more flux bias control signals to the one or more tunable inductive couplers of the coupling busto mediate interactions between the first and second qubitsand, using techniques as discussed in further detail below. In some embodiments, the qubit drive linesandare coupled (e.g., capacitively coupled) to the first and second qubitsand, respectively. In some embodiments, the qubit drive linesandare configured to apply control signals (e.g., microwave control pulse signals) to independently change the states of the respective first and second qubitsand.

112 110 110 122 120 120 1 1 For example, a microwave control pulse can be applied to the qubit drive lineto perform a single-qubit gate operation on the first qubitor otherwise modify the computational state of the first qubitas needed when executing a quantum algorithm. Furthermore, a microwave control pulse can be applied to the qubit drive lineto perform a single-qubit gate operation on the second qubitor otherwise modify the computational state of the second qubitas needed when executing a quantum algorithm. As is known in the art, the state of a qubit can be changed by applying a microwave control signal (e.g., control pulse) with a center frequency equal to a transition frequency (denoted f) of the qubit, wherein the transition frequency fcorresponds to an energy difference between the ground state |0and excited state |1of the qubit. In addition, the axis of rotation about a given axis of the Bloch sphere (e.g., X-axis, Y-axis, or any axis in the X-Y plane) and the amount (angle) of such rotation are based, respectively, on the phase of the microwave control signal, and the amplitude and duration of the microwave control signal.

114 124 110 120 114 124 110 120 Further, in some embodiments, the qubit readout resonatorsandare dispersively coupled to the first and second qubitsand, respectively, using known techniques to perform dispersive readout operations. In some embodiments, the qubit readout resonatorsandcomprise transmission line readout resonators (e.g., coplanar waveguide (CPW) resonators) which are configured to have resonant frequencies that are detuned from the respective transition frequencies of respective first and second qubitsand. In the dispersive regime of qubit-resonator coupling, an RF readout control signal (with the requisite frequency tone, pulse envelope shape, and pulse duration) is applied to a given readout resonator of a given qubit-resonator circuit, and interacts with the given qubit-resonator circuit in a manner which results in the generation of a readout signal that is reflected out from the given readout resonator. The readout signal comprises information (e.g., phase and amplitude information) that is qubit-state dependent. In this regard, a dispersive readout process yields an RF readout signal having a state-dependent phasor response, which is analyzed to discriminate the quantum state of the given qubit, e.g., determine whether the readout state of the given qubit is the ground state |0or the first excited state |1, wherein for readout, a superposition state of the given qubit is projected onto the ground state |0or the first excited state |1, as is known in the art.

130 132 130 130 1 FIG. 2 5 6 7 8 FIGS.,,,, and It is to be noted that the coupling busincan be implemented using various configurations of components including transmission line resonators that are coupled together using flux-tunable inductive couplers, or a combination of flux-tunable inductive couplers and fixed coupling components (coupling capacitors and/or coupling inductors). In general, each of the flux-tunable inductive couplers can be implemented using any suitable superconducting flux-tunable superconducting device having one or more tunable inductive elements (e.g., one or more Josephson junctions) that can be flux-tuned (via the control signals applied to the flux bias control lines) into different impedance states to control an amount of inductive coupling between adjacent transmission line resonators of the coupling bus. For example, in some embodiments, the flux-tunable inductive couplers are implemented using radio frequency superconducting quantum interference devices (RF-SQUIDs). In other embodiments, the flux-tunable inductive couplers are implemented using direct current superconducting quantum interference devices (DC-SQUIDs). In other embodiments, the flux-tunable inductive couplers can be implemented using other types of flux-tunable devices which comprise a superconducting loop comprising one or more Josephson junctions which have non-linear inductances that are modulated by an amount of magnetic flux bias that threads through the superconducting loop to change the inductance of the flux-tunable inductive coupler. In this regard, various embodiments of the coupling buswill be discussed in further detail below in conjunction with, e.g.,.

2 FIG. 2 FIG. 200 202 202 210 220 230 210 220 210 220 For example,schematically illustrates a system comprising a quantum device which comprises a coupling bus that is configured to mediate interactions between quantum bits, according to an exemplary embodiment of the disclosure. In particular,schematically illustrates a quantum systemwhich comprises a quantum chipand various components disposed on the quantum chip, where such components include, but are not limited to, a first qubit, a second qubit, and a coupling busthat is coupled to and between the first and second qubitsand. In some embodiments, the first and second qubitsandcomprise fixed-frequency superconducting transmon qubits. In general, a transmon qubit comprises a Josephson junction and capacitor that are connected in parallel, wherein the Josephson junction functions as a non-linear inductor which, when shunted with the capacitor, forms an anharmonic LC oscillator with individually addressable energy levels (e.g., two lowest energy levels corresponding to the ground state |0and the first excited state |1).

2 FIG. 210 211 212 213 211 212 211 212 213 220 221 222 223 221 222 221 222 223 As schematically illustrated in, the first qubitcomprises a first superconducting pad, a second superconducting pad, and a Josephson junctionthat is coupled to, and disposed between, the first and second superconducting padsand. The first and second superconducting padsandcomprise electrodes of a coplanar capacitor structure which is connected in parallel with the Josephson junctionto form a transmon-type qubit. Similarly, the second qubitcomprises a first superconducting pad, a second superconducting pad, and a Josephson junctionthat is coupled to, and disposed between, the first and second superconducting padsand. The first and second superconducting padsandcomprise electrodes of a coplanar capacitor structure which is connected in parallel with the Josephson junctionto form a transmon-type qubit.

230 240 240 240 240 240 240 250 250 250 250 250 240 240 240 240 240 240 250 250 250 250 250 250 230 210 220 210 240 240 240 250 240 240 250 240 240 250 240 240 250 240 240 250 220 240 1 2 3 4 5 6 1 2 3 4 5 1 2 3 4 5 6 1 2 3 4 5 6 C1 1 1 2 1 2 3 2 3 4 3 4 5 4 5 6 5 C2 6 C1 C2 2 FIG. The coupling buscomprises a plurality of transmission line resonators,,,,, and, and a plurality of flux-tunable inductive couplers,,,, and. The transmission line resonators,,,,, and, and the flux-tunable inductive couplers,,,,, andare serially connected in an alternating manner to form the coupling busbetween the first and second qubitsand. In particular, as schematically shown in, the first qubitis capacitively coupled (via a coupling capacitor C) to the first transmission line resonator. The first transmission line resonatorand the second transmission line resonatorare coupled by the first flux-tunable inductive coupler. The second transmission line resonatorand the third transmission line resonatorare coupled by the second flux-tunable inductive coupler. The third transmission line resonatorand the fourth transmission line resonatorare coupled by the third flux-tunable inductive coupler. The fourth transmission line resonatorand the fifth transmission line resonatorare coupled by the fourth flux-tunable inductive coupler. The fifth transmission line resonatorand the sixth transmission line resonatorare coupled by the fifth flux-tunable inductive coupler. The second qubitis capacitively coupled (via a coupling capacitor C) to the sixth transmission line resonator. The coupling capacitors Cand Ccan be implemented using suitable capacitive coupling structures and techniques known to those of ordinary skill in the art.

240 240 240 240 240 240 240 240 240 240 240 240 240 240 240 240 240 240 240 240 240 240 240 240 210 220 240 240 240 240 240 240 210 220 1 2 3 4 5 6 1 2 3 4 5 6 1 2 3 4 5 6 1 2 3 4 5 6 1 2 3 4 5 6 In some embodiments, the transmission line resonators,,,,, andcomprise nominally identical CPW resonators which have the same electrical length. In some embodiments, the transmission line resonators,,,,, andeach comprise an open-circuited half-wavelength (λ/2) transmission line resonator with a length l=(n×λ)/2, wherein n denotes a resonant mode number (n=1, 2, 3, . . . ). In a non-limiting exemplary embodiment, the transmission line resonators,,,,, andeach have a resonator length of approximately 4.1 millimeters (mm) and a fundamental resonant frequency of about 6.0 GHz. In some embodiments, the transmission line resonators,,,,, andare configured to have a same nominal resonant frequency which is greater than the transition frequencies of the first and second qubitsand. In other embodiments, the transmission line resonators,,,,, andare configured to have a same nominal resonant frequency which is less than the transition frequencies of the first and second qubitsand.

200 260 250 250 250 250 250 230 210 220 250 250 250 250 250 250 250 250 250 250 1 2 3 4 5 1 2 3 4 5 C1 C2 C3 C4 C5 C1 C2 C3 C4 C5 1 2 3 4 5 1 2 3 4 5 C1 C2 C3 C4 C5 BIAS 1 2 3 4 5 2 FIG. The quantum systemfurther comprises a flux bias control signal generatorwhich is configured to generate a plurality of flux bias control signals, Flux_Con1, Flux_Con2, Flux_Con3, Flux_Con4, and Flux_Con5 for controlling the flux-tunable inductive couplers,,,, and, respectively, to thereby control the operation of the coupling busfor mediating interactions between the first and second qubitsand. As schematically illustrated in, the flux-tunable inductive couplers,,,, andare disposed adjacent to respective coupling inductors L, L, L, L, and L. Each coupling inductor L, L, L, L, and Lis connected in series (inline) with a respective control line C, C, C, C, and C. The flux bias control signals Flux_Con1, Flux_Con2, Flux_Con3, Flux_Con4, and Flux_Con5 are applied to the respective control lines C, C, C, C, and C. In some embodiments, the flux bias control signals Flux_Con1, Flux_Con2, Flux_Con3, Flux_Con4, and Flux_Con5 comprise control currents which flow through the respective coupling inductors L, L, L, L, and Lto generate magnetic fluxes (denoted Φ) for tuning the flux-tunable inductive couplers,,,, andinto desired operating states.

250 250 250 250 250 250 250 250 250 250 1 2 1 2 3 4 5 BIAS 1 2 3 4 5 Bias 2 FIG. In particular, each flux-tunable inductive coupler,,,, andcomprises a superconducting loop which comprises at least one Josephson junction having a non-linear inductance that is modulated by a magnetic flux bias Φwhich threads through the superconducting loop to change the inductance and thereby selectively place a flux-tunable inductive coupler into one of two different operating states, which are referred to herein as an “ON state” and an “OFF state.” In some embodiments, as schematically illustrated in, the flux-tunable inductive couplers,,,, andcomprise nominally identical RF-SQUIDs, where each RF-SQUID comprises a series Josephson junction JJ, a first superconducting inductor L, and a second superconducting inductor L, which are connected to form a superconducting loop through which a given magnitude of magnetic flux bias Φis threaded to selectively place the RF-SQUID into an ON state or an OFF state.

Bias Bias For example, to place a given flux-tunable inductive coupler into an ON state, a flux bias control signal is applied to the associated control line to cause a first amount of magnetic flux bias Φto thread through the superconducting loop of the given flux-tunable inductive coupler and place the given flux-tunable inductive coupler into a first inductance state in which the given flux-tunable inductive coupler is activated (placed into ON state) to turn on a coupling between adjacent transmission line resonators coupled to the given flux-tunable inductive coupler. On the other hand, to place the given flux-tunable inductive coupler into an OFF state, a flux bias control signal is applied to the associated control line to cause a second amount of magnetic flux bias Φto thread through the superconducting loop of the given flux-tunable inductive coupler and place the given flux-tunable inductive coupler into a second inductance state in which the given flux-tunable inductive coupler is deactivated (placed into OFF state) to turn off an inductive coupling between the adjacent transmission line resonators coupled to the given flux-tunable inductive coupler.

230 240 240 240 240 240 240 240 240 240 240 240 240 250 250 250 250 250 250 250 250 250 250 240 240 240 240 240 240 230 210 220 230 210 220 2 FIG. 1 2 3 4 5 6 1 2 3 4 5 6 1 2 3 4 5 1 2 3 4 5 1 2 3 4 5 6 More specifically, in the exemplary configuration of the coupling busshown in, the transmission line resonators,,,,, andare designed to have nominally identical resonator lengths, wherein the resonator length is selected so that each transmission line resonator,,,,, andhas a nominally identical resonant frequency and frequency range, when the flux-tunable inductive couplers,,,, andare tuned in an OFF state. When all flux-tunable inductive couplers,,,, andare tuned in the OFF state, there is no inductive coupling between any adjacent pairs of the transmission line resonators,,,,, andand, consequently, the coupling busis in an OFF state in which there is no coupling (e.g., no exchange coupling) between the first qubitand the second qubit. With the coupling busin an OFF state, the exchange coupling (or residual ZZ coupling) between the first and second qubitsandis significantly suppressed.

250 250 250 250 250 250 250 250 250 250 240 240 240 240 240 240 250 250 250 250 250 240 240 240 240 240 240 210 220 210 220 210 220 230 230 210 220 1 2 3 4 5 1 2 3 4 5 1 2 3 4 5 6 1 2 3 4 5 1 2 3 4 5 6 On the other hand, when all flux-tunable inductive couplers,,,, andare tuned into an ON state, the flux-tunable inductive couplers,,,, andprovide inductive coupling between adjacent pairs of the transmission line resonators,,,,, and. The inductive coupling through the flux-tunable inductive couplers,,,, andcauses the individual modes of the transmission line resonators,,,,, andto hybridize with each other, thereby resulting in one of the normal modes of the hybridized resonators to move toward the transition frequencies of the first and second qubitsandwhich, in turn, significantly increases the exchange coupling between the first and second qubitsand, e.g., significantly increasing the ZZ interaction between the first and second qubitsandthrough the coupling bus. The strong ZZ interaction through the coupling busenables a fast two-qubit gate operation (e.g., Controlled-Phase gate) between the first and second qubitand.

230 210 220 240 240 240 240 240 240 240 240 240 240 240 240 210 220 240 240 240 240 240 240 210 220 250 250 250 250 250 210 220 230 240 240 240 240 240 240 210 220 1 2 3 4 5 6 1 2 3 4 5 6 1 2 3 4 5 6 1 2 3 4 5 1 2 3 4 5 6 It is to be noted that the operating mode of the coupling buswill vary depending on the transition frequencies of the first and second qubitsandand the normal frequency modes of the transmission line resonators,,,,, and. For example, in some embodiments, the transmission line resonators,,,,, andare designed to have a nominally identical resonant frequency which is greater than the respective transition frequencies of the first and second qubitsand. In other embodiments, the transmission line resonators,,,,, andare designed to have a nominally identical resonant frequency which is less than the respective transition frequencies of the first and second qubitsand. Furthermore, the manner in which the flux-tunable inductive couplers,,,, andare tuned into ON and OFF states to control and mediate the exchange coupling (e.g., ZZ interaction) between the first and second qubitsandthrough the coupling buswill vary depending on whether the normal mode resonant frequency of each transmission line resonator,,,,, andis greater than or less than the respective transition frequencies of the first and second qubitsand.

2 FIG. 250 250 250 250 250 250 250 250 250 250 250 250 250 250 250 1 2 3 4 5 1 2 3 4 5 Bias BIAS 0 0 0 1 2 3 4 5 BIAS 0 For example, in the exemplary embodiment ofwhere the flux-tunable inductive couplers,,,, andcomprise nominally identical RF-SQUIDS, each flux-tunable inductive coupler,,,, andcan be placed into an OFF state by applying a magnetic flux bias Φthrough the superconducting loop of the RF-SQUID, which has a magnitude of Φ=xΦ, where x is a value between 0 and 0.5, and where Φdenotes the magnetic flux quantum Φ=h/2e (where h denotes the Planck constant and e denotes the elementary charge constant). In an exemplary non-limiting embodiment, the flux-tunable inductive couplers,,,, andcan be designed such that a given flux-tunable inductive coupler is placed into an OFF state by applying a magnetic flux bias of Φ≈0.25 Φthrough the superconducting loop thereof. As noted above, when a given flux-tunable inductive coupler is placed into an OFF state, there is no inductive coupling between adjacent transmission line resonators coupled to the given flux-tunable inductive coupler.

BIAS BIAS 1 2 3 4 5 BIAS 0 1 2 250 250 250 250 250 It is to be noted that the precise amount of magnetic flux bias Φto place a given flux-tunable inductive coupler (implemented as an RF-SQUID) into an OFF state corresponds to the amount of magnetic flux bias Φwhich results in no (zero) inductive coupling across the single Josephson junction JJ of the RF-SQUID, wherein the precise value depends on the size of the Josephson junction JJ and the size of the inductors Land Lwhere a net-zero inductive coupling is achieved where the inductance of the Josephson junction JJ cancels out the geometric inductance of the RF SQUID (where the geometric inductance is based in part on the shape and dimensions of the superconducting SQUID loop). In some embodiments, the RF-SQUIDs that implement the flux-tunable inductive couplers,,,, andare designed to have an OFF state in response to a magnetic flux bias of Φ≈0.25 Φ.

BIAS 0 BIAS 0 1 2 3 4 5 6 1 2 3 4 5 6 BIAS BIAS 0 1 6 BIAS BIAS 240 240 240 240 240 240 210 220 240 240 240 240 240 240 210 220 240 240 210 220 On the other hand, a given flux-tunable inductive coupler can be placed into an ON state by either increasing the magnetic flux bias to a magnitude of Φ>0.25 Φor decreasing the magnetic flux bias to a magnitude of Φ<0.25 Φ, depending on whether the nominally identical resonant frequency of the transmission line resonators,,,,, andis greater than or less than the transition frequencies of the first and second qubitsand. In particular, in embodiments where the normal mode resonant frequency of the transmission line resonators,,,,, andis greater than the transition frequencies of the first and second qubitsand, a given flux-tunable inductive coupler can be placed into an ON state by increasing the magnetic flux bias Φto a magnitude of Φ≈0.5 Φ. On the other hand, in embodiments where the normal mode resonant frequency of the transmission line resonators-is less than the transition frequencies of the first and second qubitsand, a given flux-tunable inductive coupler can be placed into an ON state by decreasing the magnetic flux bias Φto a magnitude of Φ≈0.

240 240 240 240 240 240 210 220 210 220 202 210 220 230 210 220 250 250 250 250 250 250 250 250 250 250 240 240 240 240 240 240 230 1 2 3 4 5 6 BIAS 0 1 2 3 4 5 1 2 3 4 5 1 2 3 4 5 6 By way of example, assume that that the transmission line resonators,,,,, andare each designed to have a normal mode resonant frequency of 6.0 GHz, and that the first and second qubitsandare designed to have respective transition frequencies in a range of 4.5 GHz to 5.5 GHz. Depending on the location of the first and second qubitsandin a given qubit array on the quantum chip, the first and second qubitsandcan be designed to have the same transition frequency or different transition frequencies, where the transition frequencies are selected to avoid frequency collisions within the given qubit array, as is understood by those of ordinary skill in the art. In this exemplary configuration, the coupling buscan be turned ON to achieve a strong exchange coupling between the first and second qubitsandby applying a magnetic flux bias of Φ≈0.5 Φto each of the flux-tunable inductive couplers,,,, andto thereby place each flux-tunable inductive coupler,,,, andinto an ON state and turn on the inductive coupling between the transmission line resonators,,,,, andof the coupling bus.

250 250 250 250 250 240 240 240 240 240 240 230 240 240 240 240 240 240 240 240 240 240 240 240 210 220 210 220 230 1 2 3 4 5 1 2 3 4 5 6 1 2 3 4 5 6 1 2 3 4 5 6 In this exemplary configuration, placing each of the flux-tunable inductive couplers,,,, andinto an ON state serves to enable inductive coupling between the transmission line resonators,,,,, andover the coupling buswhich, in turn, causes the normal modes of the transmission line resonators,,,,, andto be hybridized. As a result of mode hybridization, one of the normal modes (e.g., lowest frequency mode) of the hybridized transmission line resonators,,,,, andmoves down in frequency (e.g., lowest hybridized frequency mode) towards the transition frequencies of the first and second qubitsand, which results in a strong exchange coupling between the first and second qubitsandvia the coupling bus.

240 240 240 240 240 240 210 220 240 240 240 240 240 240 240 240 240 240 240 240 210 220 1 2 3 4 5 6 1 2 3 4 5 6 1 2 3 4 5 6 By way of example, assuming the transmission line resonators,,,,, andhave a resonant frequency of 6.0 GHz, and the first and second qubitsandeach have a transition frequency of 5.0 GHz, the lowest hybridized frequency mode of the transmission line resonators,,,,, and(which is generated as a result of the inductive coupling) can be around 5.1 GHz. In this instance, the qubit-resonator exchange coupling is about 100 MHz. Moreover, the other hybridized modes (higher frequency modes) of the transmission line resonators,,,,, andwill remain above, e.g., 7.0 GHz. As such, the higher frequency hybridized modes will not dephase the first and second qubitsand. In addition, the higher frequency hybridized modes are less likely to be thermally populated in the typical cryogenic temperature environments of dilution refrigerators.

230 240 240 210 220 210 220 240 240 240 240 240 240 230 210 220 250 250 250 250 250 250 250 250 250 250 240 240 240 240 240 240 230 1 6 1 2 3 4 5 6 BIAS 0 1 2 3 4 5 1 2 3 4 5 1 2 3 4 5 6 In other embodiments, as noted above, the coupling buscan be designed where normal mode resonant frequency of the transmission line resonators-is less than the transition frequencies of the first and second qubitsand. By way of example, assuming that first and second qubitsandeach have a transition frequency of 5.0 GHz, the transmission line resonators,,,,, andcan be designed to have nominally identical resonant frequency in a range of 3.5 GHz to 4.0 GHz. In this exemplary configuration, the coupling buscan be turned ON to achieve a strong exchange coupling between the first and second qubitsandby applying a magnetic flux bias of Φ≈0 Φto each of the flux-tunable inductive couplers,,,, andto thereby place each flux-tunable inductive coupler,,,, andinto an ON state and turn on the inductive coupling between the transmission line resonators,,,,, andof the coupling bus.

250 250 250 250 250 240 240 240 240 240 240 230 240 240 240 240 240 240 240 240 240 240 240 240 210 220 210 220 230 240 240 240 240 240 240 1 2 3 4 5 1 2 3 4 5 6 1 2 3 4 5 6 1 2 3 4 5 6 1 2 3 4 5 6 In this exemplary configuration, placing each of the flux-tunable inductive couplers,,,, andinto an ON state serves to enable inductive coupling between the transmission line resonators,,,,, andover the coupling buswhich, in turn, causes the normal modes of the transmission line resonators,,,,, andto be hybridized. As a result of mode hybridization, one of the normal modes of the hybridized transmission line resonators,,,,, andmoves up in frequency (e.g., highest frequency hybridized mode) towards the transition frequencies of the first and second qubitsand, which results in a strong exchange coupling between the first and second qubitsandvia the coupling bus. For example, a highest frequency hybridized mode of the transmission line resonators,,,,, and(which is generated as a result of the inductive coupling) can be around 4.9 or 5.0 GHz.

250 250 250 250 250 230 210 220 230 250 250 250 250 250 230 210 220 230 250 250 250 250 250 230 210 220 114 124 210 220 210 220 210 220 1 2 3 4 5 1 2 3 4 5 1 2 3 4 5 2 FIG. 1 FIG. In some embodiments, a two-qubit gate operation can be performed by a process which comprises (i) concurrently placing each flux-tunable inductive coupler,,,, andinto an ON state to turn ON the coupling busand enable strong exchange coupling (e.g., ZZ interaction) between the first and second qubitsandover the coupling bus, and (ii) concurrently placing each flux-tunable inductive couplers,,,, andinto an OFF state to complete a two-qubit gate operation and turn OFF the coupling busto suppress exchange coupling (e.g., ZZ interaction) between the first and second qubitsandover the coupling bus. In other embodiments, a two-qubit gate operation can be performed by a process which comprises tuning the flux-tunable inductive couplers,,,, andinto ON and OFF states according a specified ON and OFF sequence, which serves to prevent or otherwise suppress interaction between the modes of the coupling busand the qubit readout resonators of the first and second qubitsand(not specifically shown in). In the regime of dispersive readout of qubit states, the qubit readout resonators (e.g., qubit readout resonatorsand,) are configured to have resonant frequencies that are detuned from the respective transition frequencies of the respective first and second qubitsand. For example, assuming the first and second qubitsandeach have a transition frequency of 5.0 GHz, the associated readout resonators can each be designed to have a resonant frequency of about 7.0 GHz, which is well detuned from the transition frequency of the first and second qubitsand.

3 FIG. 3 FIG. 2 FIG. 300 230 250 250 250 250 250 230 210 220 300 250 250 250 250 250 301 302 250 250 250 250 250 303 304 1 2 3 4 5 1 2 3 4 5 1 2 3 4 5 illustrates a flow diagram of a method for utilizing a coupling bus to mediate interactions between quantum bits, according to an exemplary embodiment of the disclosure. In particular,illustrates a flow diagram of a methodto perform a two-qubit gate operation using the exemplary coupling busofwhere the flux-tunable inductive couplers,,,, andare tuned into ON and OFF states according specified ON and OFF sequences to prevent or otherwise suppress interaction between the modes of the coupling busand readout resonators of the first and second qubitsand. The methodinvolves tuning the flux-tunable inductive couplers,,,, andinto ON states in stages (blocksand), followed by tuning the flux-tunable inductive couplers,,,, andinto OFF states in stages (blocksand).

250 250 250 250 250 230 230 210 220 230 301 250 250 250 250 250 1 2 3 4 5 2 3 4 1 5 2 FIG. In particular, to commence a two-qubit gate operation, starting with each flux-tunable inductive coupler,,,, andin an OFF state (deactivated), an initial step involves placing each flux-tunable inductive coupler in the middle (interior) portion of the coupling businto an ON state to enable coupling of the transmission line resonators in the middle portion of the coupling bus, while maintaining the first and second qubitsanddecoupled from the coupling bus(block). For example, in the exemplary embodiment of, the initial step involves placing the flux-tunable inductive couplers,, andinto an ON state, while initially leaving the flux-tunable inductive couplersandin an OFF state.

301 240 240 240 240 250 250 250 240 240 240 240 240 240 240 240 210 220 301 250 250 210 220 210 220 2 3 4 5 2 3 4 2 3 4 5 2 3 4 5 1 5 The initial step (block) results in the inductive coupling of the transmission line resonators,,, and(through the flux-tunable inductive couplers,, andin the ON states), which, in turn, causes the normal modes of the inductively-coupled transmission line resonators,,, andto be hybridized as discussed above, where as a result of mode hybridization, one of the normal modes (e.g., lowest frequency mode) of the hybridized transmission line resonators,,, andmoves down in frequency (e.g., lowest hybridized frequency mode) towards the transition frequencies of the first and second qubitsand. Moreover, with this initial step (block), the flux-tunable inductive couplersandthat are adjacent to the respective first and second qubitsandare initially kept in the OFF state to prevent coupling between the qubit readout resonators and the coupling bus modes through the first and second qubitsandthemselves.

230 250 250 230 210 220 230 302 240 240 210 220 230 210 220 210 220 1 5 1 6 Next, after some time when it is expected that the unused hybridized modes of the coupling busare above the resonator frequencies of the qubit readout resonators, the process proceeds to place each flux-tunable inductive coupler (e.g., flux-tunable inductive couplersand) at the ends of the coupling businto an ON state to thereby enable exchange coupling between the first and second qubitsandover the fully turned ON coupling busto perform a two-qubit gate operation (block). This process causes the modes of the transmission line resonatorsand(which are coupled to the first and second qubitsand) to hybridize and cause the lowest frequency mode of the coupling busto, e.g., move down towards the transition frequencies of the first and second qubitsand, thereby increasing the exchange coupling (e.g., ZZ interaction) between the first and second qubitsandto perform a two-qubit gate operation.

210 220 210 220 The two-qubit gate operation can be, e.g., a Controlled-Phase gate operation (CPHASE gate) in which a phase shift is applied to a target qubit when a control qubit is in a first excited state |1. In other embodiments, when the first and second qubitsandare close in frequency, the two-qubit gate operation can be a SWAP gate operation in which the state of the first qubitbecomes the state of the second qubit, and vice versa, or any other type of parametric entanglement gate operation that can be implemented the exemplary long-range qubit coupling architectures as discussed herein.

210 220 250 250 250 210 220 250 250 230 210 220 230 303 250 250 250 230 304 240 240 240 240 240 240 210 220 230 2 3 4 1 5 2 3 4 1 2 3 4 5 6 Upon completion of the gate operation, the first and second qubitsandare decoupled by placing the flux-tunable inductive couplers,, andinto OFF states using a turn OFF sequence which is opposite (reverse order) to the turn ON sequence. More specifically, to terminate the gate operation and decouple the first and second qubitsand, an initial step involves placing each flux-tunable inductive coupler (e.g., flux-tunable inductive couplersand) at the ends of the coupling businto an OFF state to suppress (or turn off) the exchange coupling between the first and second qubitsandover the coupling bus(block), which is then followed by placing each of the remaining flux-tunable inductive couplers,, and(in the middle portion of the coupling bus) into an OFF state (block), resulting in decoupling to an ON state, which results in decoupling the transmission line resonators,,,,, andfrom each other and, thus, significantly suppressing (or otherwise eliminating) any residual ZZ interaction between the first and second qubitsandover the coupling bus.

4 FIG. 4 FIG. 2 FIG. 21 1 2 3 4 5 1 2 3 4 5 6 400 250 250 250 250 250 210 220 240 240 240 240 240 240 depicts simulated scattering parameters with regard to signal transmission between qubits over a coupling bus, according to an exemplary embodiment of the disclosure. In particular,depicts simulated Sscattering parametersof a computer simulated coupling bus having an exemplary architecture as shown in, where the flux-tunable inductive couplers,,,, andare modeled as RF-SQUIDs with a superconducting loop inductance L˜0.5 nH, the first and second qubitsandare modeled as transmon qubits with transition frequencies of 5 GHz, and the transmission line resonators,,,,, andare modeled as CPW resonators with lengths of 4.1 mm.

4 FIG. 410 420 250 250 250 250 250 250 250 250 250 250 21 21 1 2 3 4 5 1 2 3 4 5 illustrates (i) a first curvewhich represents the simulated Sparameters of signal transmission over the coupling bus between the first and second transmon qubits for a frequency range of 1.0 GHz to 10.0 GHz, with the coupling bus in an ON state, and (ii) a second curvewhich represents the simulated Sparameters of signal transmission over the coupling bus between the first and second transmon qubits for the frequency range of 1.0 GHz to 10.0 GHz, with the coupling bus in an OFF state. In the ON state of the coupling bus, all the flux-tunable inductive couplers,,,, andare tuned in an ON state. In the OFF state of the coupling bus, all the flux-tunable inductive couplers,,,, andare tuned in an OFF state.

420 420 1 250 250 250 250 250 410 410 1 410 2 410 3 410 4 250 250 250 250 250 410 1 410 410 2 410 3 410 3 410 2 410 3 410 4 21 1 2 3 4 5 21 1 2 3 4 5 21 21 21 21 The second curvecomprises a point-which illustrates a peak Stransmission at a fundamental resonant frequency mode of 6.0 GHz of the CPW resonators, when the coupling bus is in an OFF state (with all the flux-tunable inductive couplers,,,, andin an OFF state). On the other hand, the first curvecomprises various points-,-,-, and-which illustrate peak Stransmissions at different hybridized frequency modes of the CPW resonators, when the coupling bus is in an ON state (with all the flux-tunable inductive couplers,,,, andin an ON state). In particular, a first point-illustrates a peak Stransmission at the lowest hybridized frequency mode of 5.1 GHz, which enables exchange interaction between the first and second qubits over the coupling bus. In addition, the first curvecomprises a second point-which illustrates a peak Stransmission at a higher hybridized frequency mode of about 7.1 GHz, a third point-which illustrates a peak Stransmission at a higher hybridized frequency mode of about 8.1 GHz, and a fourth point-which illustrates a peak Stransmission at a higher hybridized frequency mode of about 9.3 GHz. The higher hybridized frequency modes represented by the second, third, and fourth points-,-, and-do not enable exchange interaction between the first and second qubits over the coupling bus.

2 FIG. Whileillustrates an exemplary configuration of a long-range coupling bus comprising five (5) flux-tunable inductive couplers and six (6) transmission line resonators, it is to be understood that a long-range coupling bus can be constructed using any suitable number of flux-tunable inductive couplers and transmission line resonators, depending on, e.g., the distance of a desired coupling path between two qubits within a given qubit lattice which need to be coupled together.

5 FIG. 5 FIG. 500 502 502 510 520 530 510 520 510 520 510 511 512 513 520 521 522 523 For example,schematically illustrates a device which comprises a coupling bus that is configured to mediate interactions between quantum bits, according to another exemplary embodiment of the disclosure. In particular,schematically illustrates a devicewhich comprises a quantum chipand various components disposed on the quantum chip, where such components include, but are not limited to, a first qubit, a second qubit, and a coupling busthat is coupled to and between the first and second qubitsand. In some embodiments, the first and second qubitsandcomprise fixed-frequency superconducting transmon qubits, wherein the first qubitcomprises a first superconducting pad, a second superconducting pad, and a Josephson junction, and the second qubitcomprises a first superconducting pad, a second superconducting pad, and a Josephson junction.

530 540 540 540 540 550 550 550 530 230 530 510 520 1 2 3 4 1 2 3 2 FIG. The coupling buscomprises a plurality (four) of transmission line resonators,,, and(e.g., CPW resonators), and a plurality (three) of flux-tunable inductive couplers,, and(e.g., RF-SQUIDs). The coupling busis similar in structure and operation as the coupling busdiscussed above in conjunction with(the details of which will not be repeated), except that the coupling buscomprises a smaller number of transmission line resonators and flux-tunable inductive couplers, to enable long-range coupling of the first and second qubitsand.

530 540 540 550 550 550 230 5 FIG. 2 FIG. 2 3 3 1 3 In other embodiments, a coupling bus can be constructed with two flux-tunable inductive couplers and three transmission line resonators. For example, the exemplary coupling busofcan be modified by replacing the transmission line resonatorsand, and the flux-tunable inductive couplerwith a single transmission line resonators that is coupled to and between the flux-tunable inductive couplersand. In other embodiments, the coupling busofcan be modified by adding one or more additional flux-tunable inductive couplers and transmission line resonators to construct a longer-range coupling comprising an alternating sequence of six (6) flux-tunable inductive couplers and seven (7) transmission line resonators, etc.

In this regard, it is to be noted that various exemplary embodiments of long-range coupling buses are constructed using multiple smaller lengths of transmission line resonators (e.g., multiple CPW segments) instead of one or two long transmission line resonators, to limit the number of low frequency modes. Advantageously, the use of multiple smaller-length transmission line resonators serves to custom tailor the mode structure of the coupling bus so that only one hybridized frequency mode, which is close to the transition frequencies of the qubits, is generated on the coupling bus to enable exchange coupling between the qubits, while all other hybridized frequency modes are detuned far from the transition frequencies of the qubits.

6 FIG. 6 FIG. 600 602 602 610 620 630 610 620 610 620 610 611 612 613 620 621 622 623 In other embodiments, as noted above, long-range qubit-qubit exchange interactions can be mediated using coupling buses which comprise multiple transmission line resonators that are coupled together using a combination of flux-tunable inductive couplers and fixed coupling components (coupling capacitors and/or coupling inductors). For example,schematically illustrates a device which comprises a coupling bus that is configured to mediate interactions between quantum bits, according to another exemplary embodiment of the disclosure, in which the coupling bus comprises multiple transmission line resonators that are coupled together using flux-tunable inductive couplers and fixed coupling capacitors. In particular,schematically illustrates a devicewhich comprises a quantum chipand various components disposed on the quantum chip, where such components include, but are not limited to, a first qubit, a second qubit, and a coupling busthat is coupled to and between the first and second qubitsand. In some embodiments, the first and second qubitsandcomprise fixed-frequency superconducting transmon qubits, wherein the first qubitcomprises a first superconducting pad, a second superconducting pad, and a Josephson junction, and the second qubitcomprises a first superconducting pad, a second superconducting pad, and a Josephson junction.

630 640 640 640 640 640 640 650 650 655 655 655 630 230 630 655 655 655 250 250 250 230 630 640 640 640 640 655 655 655 630 650 650 1 2 3 4 5 6 1 2 1 2 3 1 2 3 2 3 4 2 3 4 5 1 2 3 1 2 2 FIG. 2 FIG. 6 FIG. The coupling buscomprises a plurality of transmission line resonators,,,,, and(e.g., CPW resonators), a plurality of flux-tunable inductive couplersand(e.g., RF-SQUIDs), and a plurality of fixed coupling capacitors,, and. The coupling busis similar in structure and operation as the coupling busdiscussed above in conjunction with, except that the coupling busimplements the fixed coupling capacitors,, andin place of the flux-tunable inductive couplers,, andof the coupling bus(). In the exemplary configuration of the coupling busof, the coupling between the transmission line resonators,,, andis always “ON” by virtue of the fixed capacitive coupling provided by the fixed coupling capacitors,, and, while the activation (turning ON) and deactivation (turning OFF) of the coupling busis controlled by tuning the flux-tunable inductive couplersandinto ON states and OFF states using flux tuning techniques as discussed above.

7 FIG. 7 FIG. 700 702 702 710 720 730 710 720 710 720 710 711 712 713 720 721 722 723 Next,schematically illustrates a device which comprises a coupling bus that is configured to mediate interactions between quantum bits, according to another exemplary embodiment of the disclosure, in which the coupling bus comprises multiple transmission line resonators that are coupled together using flux-tunable inductive couplers and fixed coupling inductors. In particular,schematically illustrates a devicewhich comprises a quantum chipand various components disposed on the quantum chip, where such components include, but are not limited to, a first qubit, a second qubit, and a coupling busthat is coupled to and between the first and second qubitsand. In some embodiments, the first and second qubitsandcomprise fixed-frequency superconducting transmon qubits, where the first qubitcomprises a first superconducting pad, a second superconducting pad, and a Josephson junction, and where the second qubitcomprises a first superconducting pad, a second superconducting pad, and a Josephson junction.

730 740 740 740 740 740 740 750 750 755 755 755 730 630 730 755 755 755 655 655 655 630 730 740 740 740 740 755 755 755 730 750 750 1 2 3 4 5 6 1 2 1 2 3 1 2 3 1 2 3 2 3 4 5 1 2 3 1 2 6 FIG. 6 FIG. 7 FIG. The coupling buscomprises a plurality of transmission line resonators,,,,, and(e.g., CPW resonators), a plurality of flux-tunable inductive couplersand(e.g., RF-SQUIDs), and a plurality of fixed coupling inductors,, and. The coupling busis similar in structure and operation as the coupling busof, except that the coupling busimplements the fixed coupling inductors,, andin place of the fixed coupling capacitors,, andof the coupling bus(). In the exemplary configuration of the coupling busof, the coupling between the transmission line resonators,,, andis always “ON” by virtue of the fixed inductive coupling provided by the fixed coupling inductors,, and, while the activation (turning ON) and deactivation (turning OFF) of the coupling busis controlled by tuning the flux-tunable inductive couplersandinto ON states and OFF states using flux tuning techniques as discussed above.

630 730 530 550 6 7 FIGS.and 6 7 FIGS.and 5 FIG. 2 The exemplary configurations of the coupling busesandas shown ininclude a series of transmission line resonators which are coupled using a fixed coupling through fixed coupling capacitors or inductors, and dynamic, tunable inductive coupling through flux-tunable inductive couplers. While the exemplary embodiments of the coupling buses shown incomprises six (6) transmission line resonators, two (2) flux-tunable inductive couplers, and four (4) fixed coupling elements, it is to be understood that other embodiments of long-range coupling buses can be constructed using more or less of any of transmission line resonators, flux-tunable inductive couplers, and fixed coupling elements, as desired for a given application. By way of example, a long-range coupling bus can be implemented which is similar in structure to the coupling busshown in, where the flux-tunable inductive coupleris replaced with a fixed coupling capacitor or a fixed coupling inductor. It is to be further noted that in other exemplary embodiments, a long-range coupling bus can be implemented using a single flux-tunable inductive coupler that is disposed between two adjacent transmission line resonators at any point of the coupling bus, e.g., adjacent to a given qubit, or in the middle portion of the coupling bus. However, implementing two or more flux-tunable inductive couplers in a coupling bus provides better tunability and control of qubit-qubit exchange interactions.

8 FIG. 8 FIG. 800 802 802 810 820 830 810 820 810 820 810 811 812 813 820 821 822 823 Moreover, while the exemplary coupling bus embodiments discussed above utilize RF-SQUIDs to implement the flux-tunable inductive couplers, in other embodiments, lone-range coupling buses can be constructed using other types of flux-tunable inductive components to provide dynamic, tunable inductive coupling of adjacent transmission line resonators of the coupling bus. For example,schematically illustrates a device which comprises a coupling bus that is configured to mediate interactions between quantum bits, according to another exemplary embodiment of the disclosure, in which the coupling bus utilizes DC-SQUIDs as flux-tunable inductive couplers to control inductive coupling between adjacent transmission line resonators. In particular,schematically illustrates a devicewhich comprises a quantum chipand various components disposed on the quantum chip, where such components include, but are not limited to, a first qubit, a second qubit, and a coupling busthat is coupled to and between the first and second qubitsand. In some embodiments, the first and second qubitsandcomprise fixed-frequency superconducting transmon qubits, where the first qubitcomprises a first superconducting pad, a second superconducting pad, and a Josephson junction, and where the second qubitcomprises a first superconducting pad, a second superconducting pad, and a Josephson junction.

830 840 840 840 840 850 850 850 830 530 830 850 850 850 1 2 1 2 3 4 1 2 3 1 2 3 5 FIG. 8 FIG. The coupling buscomprises a plurality of transmission line resonators,,, and(e.g., CPW resonators), and a plurality of flux-tunable inductive couplers,, andwhich are implemented using nominally identical DC-SQUIDs. The exemplary coupling busis similar in structure and operation as the coupling busdiscussed above in conjunction with, except that the coupling busutilizes DC-SQUIDs to implement the flux-tunable inductive couplers,, andinstead of RF-SQUIDs, to dynamically control the inductive coupling between adjacent transmission line resonators. As schematically shown in, each DC-SQUID comprises a comprises a superconducting loop which comprises two Josephson junctions including a first Josephson junction Jand a second Josephson junction J, which have non-linear inductances.

8 FIG. 850 850 850 850 850 850 1 2 3 C1 C2 C3 C1 C2 C3 1 2 3 1 2 3 BIAS As schematically illustrated in, similar to the exemplary embodiment discussed above, the flux-tunable inductive couplers,, andare disposed adjacent to respective coupling inductors L, L, and L, where each coupling inductor L, L, and Lis connected in series (inline) with a respective control line C, C, and Con which respective flux bias control signals Flux_Con1, Flux_Con2, and Flux_Con3 (e.g., control currents) are applied to generate magnetic fluxes for tuning each of the flux-tunable inductive couplers,, andinto an ON state or OFF state to control the inductive coupling between adjacent transmission line resonators. The inductance of a given DC-SQUID is modulated by an amount of magnetic flux bias Φwhich threads through the superconducting loop of the DC-SQUID. In this regard, the inductance of a given DC-SQUID is modulated by flux-tuning the DC-SQUID to selectively place a flux-tunable inductive coupler into (i) an ON state to enable coupling between adjacent transmission line resonators) or (ii) an OFF state to disrupt/break the coupling between adjacent transmission line resonators.

It is to be appreciated that the exemplary coupling bus architectures as discussed herein enable long-range, highly tunable control of exchange interactions between superconducting qubits. The exemplary coupling bus architectures are designed to eliminate low-frequency modes that are normally present in long-range buses, and provide fast and high ON/OFF ratios of qubit-qubit exchange coupling by virtue of (i) separating a coupling bus into multiple segments of transmission line resonators and (ii) utilizing flux-tunable inductive couplers (e.g., RF-SQUIDs, DC-SQUIDs, etc.) to dynamically control the inductive coupling of the transmission line resonators, or utilizing a combination of flux-tunable inductive couplers and fixed interactions using fixed coupling capacitor or coupling inductors, to couple the multiple segments of transmission line resonators.

9 FIG. 9 FIG. 3 FIG. 900 910 920 930 910 912 910 914 schematically illustrates a quantum computing system which comprises a quantum processor having superconducting qubits that are coupled by long-range coupling buses, according to an exemplary embodiment of the disclosure. In particular,schematically illustrates a quantum computing systemwhich comprises a quantum computing platform, a control system, and a quantum processor(or quantum processing unit (QPU)). In some embodiments, the quantum computing platformimplements a software platform that is configured to program a quantum computer to execute quantum computing algorithmswhich are implemented using, e.g., quantum circuits that define computational routines consisting of coherent quantum operations on quantum data, such as qubits. In addition, in some embodiments, the quantum computing platformimplements software control processesto control and synchronize the generation of flux-bias control signals (e.g.,) for controlling the operation of flux-tunable inductive couplers (e.g., RF-SQUIDs, DC-SQUIDs, etc.) of long-range coupling buses to mediate qubit-qubit exchange interactions when performing, e.g., two-qubit gate operations, as discussed herein.

920 922 924 930 932 934 In some embodiments, the control systemcomprises a multi-channel arbitrary waveform generator, and flux bias control signal generators. The quantum processorcomprises one or more solid-state quantum chip which collectively implement a superconducting qubit arraycomprising a plurality of long-range coupling buses that are configured to couple pairs of qubits, and which implement a networkof qubit drive lines, readout resonator lines, flux-bias control lines, etc., and other circuit QED components that may be needed for a given application or quantum system configuration. In some embodiments, the long-range coupling buses comprise one or more instances of the exemplary long-range coupling buses discussed above.

920 930 940 920 930 940 920 930 920 920 In some embodiments, the control systemand the quantum processorare disposed at different stages of a dilution refrigeration systemwhich can generate cryogenic temperatures that are sufficient to operate components of the control systemfor quantum computing applications. For example, the quantum processormay need to be cooled down to near-absolute zero, e.g., 10-15 millikelvin (mK), to allow the superconducting qubits to exhibit quantum behaviors. In some embodiments, the dilution refrigeration systemcomprises a multi-stage dilution refrigerator where the components of the control systemcan be maintained at different cryogenic temperatures, as needed. For example, while the quantum processormay need to be cooled down to, e.g., 10-15 mK, the circuit components of the control systemmay be operated at cryogenic temperatures greater than 10-15 mK (e.g., cryogenic temperatures in a range of 3K-4K), depending on the configuration of the quantum computing system. In other embodiments, some or all of the components of the control systemare disposed and operated in a room temperature environment.

932 932 934 920 920 930 In some embodiments, the superconducting qubit arraycomprises a quantum system of superconducting qubits, superconducting qubit couplers, and other components commonly utilized to support quantum processing using qubits. The number of superconducting qubits of the superconducting qubit arraycan be on the order of tens, hundreds, thousands, or more, etc. The networkof qubit drive lines, readout resonator lines, and flux bias control lines, etc., is coupled to the control systemthrough a suitable hardware input/output (I/O) interface, which couples I/O and control signals between the control systemand the quantum processor. For example, the hardware I/O interface may comprise various types of hardware and components, such as RF cables, wiring, RF elements, optical fibers, heat exchanges, filters, amplifiers, isolators, etc.

922 932 922 922 In some embodiments, the multi-channel AWGand other suitable microwave pulse signal generators are configured to generate the microwave control pulses that are applied to the qubit drive lines and other types of active qubit-qubit couplers (for mediated short-range qubit-qubit interactions) to control the operation of the superconducting qubits and associated qubit coupler circuitry of the superconducting qubit array, when performing various gate operations to execute a given certain quantum information processing algorithm. The multi-channel AWGgenerates and selectively applies microwave control pulses to the qubit drive lines of respective superconducting qubits to change the quantum state of the superconducting qubits (e.g., change the quantum state of a given qubit between the ground state and excited state, or to a superposition state) when executing quantum information processing algorithms. In addition, the multi-channel AWGgenerates and selectively applies microwave control pulses to qubit coupler drive lines to activate/deactivate qubit couplers that couple respective pairs of qubits to perform multi-gate entanglement operations (e.g., two qubit gate operations) when executing quantum information processing algorithms.

922 932 930 922 In some embodiments, the multi-channel AWGcomprises a plurality of AWG channels, which control respective superconducting qubits within the superconducting qubit arrayof the quantum processor. In some embodiments, each AWG channel comprises a baseband signal generator, a digital-to-analog converter (DAC) stage, a filter stage, a modulation stage, an impedance matching network, and a phase-locked loop system to generate local oscillator (LO) signals (e.g., quadrature LO signals LO_I and LO_Q) for the respective modulation stages of the respective AWG channels. In some embodiments, the multi-channel AWGcomprises a quadrature AWG system which is configured to process quadrature signals, wherein a quadrature signal comprises an in-phase (I) signal component, and a quadrature-phase (Q) signal component. In each AWG channel the baseband signal generator is configured to receive baseband data as input (e.g., from the quantum computing platform), and generate digital quadrature signals I and Q which represent the input baseband data. In this process, the baseband data that is input to the baseband signal generator for a given AWG channel is separated into two orthogonal digital components including an in-phase (I) baseband component and a quadrature-phase (Q) baseband component. The baseband signal generator for the given AWG channel will generate the requisite digital quadrature baseband IQ signals which are needed to generate an analog waveform (e.g., sinusoidal voltage waveform) with a target center frequency that is configured to operate or otherwise control a given quantum bit that is coupled to the output of the given AWG channel.

The DAC stage for the given AWG channel is configured to convert a digital baseband signal (e.g., a digital IQ signal output from the baseband signal generator) to an analog baseband signal (e.g., analog baseband signals I(t) and Q(t)) having a baseband frequency. The filter stage for the given AWG channel is configured to filter the IQ analog signal components output from the DAC stage to thereby generate filtered analog IQ signals. The modulation stage for the given AWG channel is configured to perform analog IQ signal modulation (e.g., single-sideband (SSB) modulation) by mixing the filtered analog signals I(t) and Q(t), which are output from the filter stage, with quadrature LO signals (e.g., an in-phase LO signal (LO_I) and a quadrature-phase LO signal (LO_Q)) to generate and output an analog RF signal (e.g., a single-sideband modulated RF output signal).

910 910 920 920 930 920 930 The quantum computing platformcomprises a software and hardware platform which comprises various software layers that are configured to perform various functions, including, but not limited to, generating and implementing various quantum applications using suitable quantum programming languages, configuring and implementing various quantum gate operations, compiling quantum programs into a quantum assembly language, implementing and utilizing a suitable quantum instruction set architecture (ISA), performing calibration operations to calibrate the quantum circuit elements and gate operations, etc. In addition, the quantum computing platformcomprises a hardware architecture of processors, memory, etc., which is configured to control the execution of quantum applications, and interface with the control systemto (i) generate digital control signals that are converted to analog microwave control signals by the control system, to control operations of the quantum processorwhen executing a given quantum application, and (ii) to obtain and process digital signals received from the control system, which represent the processing results generated by the quantum processorwhen executing various gate operations for a given quantum application.

910 900 10 FIG. In some exemplary embodiments, the quantum computing platformof the quantum computing systemmay be implemented using any suitable computing system architecture (e.g., as shown in) which is configured to implement methods to support quantum computing operations by executing computer readable program instructions that are embodied on a computer program product which includes a computer readable storage medium (or media) having such computer readable program instructions thereon for causing a processor to perform control methods as discussed herein.

Various aspects of the present disclosure are described by narrative text, flowcharts, block diagrams of computer systems and/or block diagrams of the machine logic included in computer program product (CPP) embodiments. With respect to any flowcharts, depending upon the technology involved, the operations can be performed in a different order than what is shown in a given flowchart. For example, again depending upon the technology involved, two operations shown in successive flowchart blocks may be performed in reverse order, as a single integrated step, concurrently, or in a manner at least partially overlapping in time.

A computer program product embodiment (“CPP embodiment” or “CPP”) is a term used in the present disclosure to describe any set of one, or more, storage media (also called “mediums”) collectively included in a set of one, or more, storage devices that collectively include machine readable code corresponding to instructions and/or data for performing computer operations specified in a given CPP claim. A “storage device” is any tangible device that can retain and store instructions for use by a computer processor. Without limitation, the computer readable storage medium may be an electronic storage medium, a magnetic storage medium, an optical storage medium, an electromagnetic storage medium, a semiconductor storage medium, a mechanical storage medium, or any suitable combination of the foregoing. Some known types of storage devices that include these mediums include: diskette, hard disk, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or Flash memory), static random-access memory (SRAM), compact disc read-only memory (CD-ROM), digital versatile disk (DVD), memory stick, floppy disk, mechanically encoded device (such as punch cards or pits/lands formed in a major surface of a disc) or any suitable combination of the foregoing. A computer readable storage medium, as that term is used in the present disclosure, is not to be construed as storage in the form of transitory signals per se, such as radio waves or other freely propagating electromagnetic waves, electromagnetic waves propagating through a waveguide, light pulses passing through a fiber optic cable, electrical signals communicated through a wire, and/or other transmission media. As will be understood by those of skill in the art, data is typically moved at some occasional points in time during normal operations of a storage device, such as during access, de-fragmentation or garbage collection, but this does not render the storage device as transitory because the data is not transitory while it is stored.

10 FIG. 10 FIG. 1000 1026 1026 1000 1001 1002 1003 1004 1005 1006 1001 1010 1020 1021 1011 1012 1013 1022 1026 1014 1023 1024 1025 1015 1004 1030 1005 1040 1041 1042 1043 1044 schematically illustrates an exemplary architecture of a computing environment for hosting a quantum computing platform and performing quantum information processing, according to an exemplary embodiment of the disclosure. The computing environmentofcontains an example of an environment for the execution of at least some of the computer code (block) involved in executing, e.g., quantum computing algorithms, and control algorithms to dynamically control the activation and deactivate of coupling buses (e.g., long range coupling buses as discussed herein). In addition to block, computing environmentincludes, for example, computer, wide area network (WAN), end user device (EUD), remote server, public cloud, and private cloud. In this embodiment, computerincludes processor set(including processing circuitryand cache), communication fabric, volatile memory, persistent storage(including operating systemand block, as identified above), peripheral device set(including user interface (UI), device set, storage, and Internet of Things (IoT) sensor set), and network module. Remote serverincludes remote database. Public cloudincludes gateway, cloud orchestration module, host physical machine set, virtual machine set, and container set.

1001 1030 1000 1001 1001 1001 10 FIG. Computermay take the form of a desktop computer, laptop computer, tablet computer, smart phone, smart watch or other wearable computer, mainframe computer, quantum computer or any other form of computer or mobile device now known or to be developed in the future that is capable of running a program, accessing a network or querying a database, such as remote database. As is well understood in the art of computer technology, and depending upon the technology, performance of a computer-implemented method may be distributed among multiple computers and/or between multiple locations. On the other hand, in this presentation of computing environment, detailed discussion is focused on a single computer, specifically computer, to keep the presentation as simple as possible. Computermay be located in a cloud, even though it is not shown in a cloud in. On the other hand, computeris not required to be in a cloud except to any extent as may be affirmatively indicated.

1010 1020 1020 1021 1010 1010 Processor setincludes one, or more, computer processors of any type now known or to be developed in the future. Processing circuitrymay be distributed over multiple packages, for example, multiple, coordinated integrated circuit chips. Processing circuitrymay implement multiple processor threads and/or multiple processor cores. Cacheis memory that is located in the processor chip package(s) and is typically used for data or code that should be available for rapid access by the threads or cores running on processor set. Cache memories are typically organized into multiple levels depending upon relative proximity to the processing circuitry. Alternatively, some, or all, of the cache for the processor set may be located “off chip.” In some computing environments, processor setmay be designed for working with qubits and performing quantum computing.

1001 1010 1001 1021 1010 1000 1026 1013 Computer readable program instructions are typically loaded onto computerto cause a series of operational steps to be performed by processor setof computerand thereby effect a computer-implemented method, such that the instructions thus executed will instantiate the methods specified in flowcharts and/or narrative descriptions of computer-implemented methods included in this document (collectively referred to as “the inventive methods”). These computer readable program instructions are stored in various types of computer readable storage media, such as cacheand the other storage media discussed below. The program instructions, and associated data, are accessed by processor setto control and direct performance of the inventive methods. In computing environment, at least some of the instructions for performing the inventive methods may be stored in blockin persistent storage.

1011 1001 Communication fabricis the signal conduction path that allow the various components of computerto communicate with each other. Typically, this fabric is made of switches and electrically conductive paths, such as the switches and electrically conductive paths that make up busses, bridges, physical input/output ports and the like. Other types of signal communication paths may be used, such as fiber optic communication paths and/or wireless communication paths.

1012 1001 1012 1001 1001 Volatile memoryis any type of volatile memory now known or to be developed in the future. Examples include dynamic type random access memory (RAM) or static type RAM. Typically, the volatile memory is characterized by random access, but this is not required unless affirmatively indicated. In computer, the volatile memoryis located in a single package and is internal to computer, but, alternatively or additionally, the volatile memory may be distributed over multiple packages and/or located externally with respect to computer.

1013 1001 1013 1013 1022 1026 Persistent storageis any form of non-volatile storage for computers that is now known or to be developed in the future. The non-volatility of this storage means that the stored data is maintained regardless of whether power is being supplied to computerand/or directly to persistent storage. Persistent storagemay be a read only memory (ROM), but typically at least a portion of the persistent storage allows writing of data, deletion of data and re-writing of data. Some familiar forms of persistent storage include magnetic disks and solid-state storage devices. Operating systemmay take several forms, such as various known proprietary operating systems or open source Portable Operating System Interface type operating systems that employ a kernel. The code included in blocktypically includes at least some of the computer code involved in performing the inventive methods.

1014 1001 1001 1023 1024 1024 1024 1001 1001 1025 Peripheral device setincludes the set of peripheral devices of computer. Data communication connections between the peripheral devices and the other components of computermay be implemented in various ways, such as Bluetooth connections, Near-Field Communication (NFC) connections, connections made by cables (such as universal serial bus (USB) type cables), insertion type connections (for example, secure digital (SD) card), connections made though local area communication networks and even connections made through wide area networks such as the internet. In various embodiments, UI device setmay include components such as a display screen, speaker, microphone, wearable devices (such as goggles and smart watches), keyboard, mouse, printer, touchpad, game controllers, and haptic devices. Storageis external storage, such as an external hard drive, or insertable storage, such as an SD card. Storagemay be persistent and/or volatile. In some embodiments, storagemay take the form of a quantum computing storage device for storing data in the form of qubits. In embodiments where computeris required to have a large amount of storage (for example, where computerlocally stores and manages a large database) then this storage may be provided by peripheral storage devices designed for storing very large amounts of data, such as a storage area network (SAN) that is shared by multiple, geographically distributed computers. IoT sensor setis made up of sensors that can be used in Internet of Things applications. For example, one sensor may be a thermometer and another sensor may be a motion detector.

1015 1001 1002 1015 1015 1015 1001 1015 Network moduleis the collection of computer software, hardware, and firmware that allows computerto communicate with other computers through WAN. Network modulemay include hardware, such as modems or Wi-Fi signal transceivers, software for packetizing and/or de-packetizing data for communication network transmission, and/or web browser software for communicating data over the internet. In some embodiments, network control functions and network forwarding functions of network moduleare performed on the same physical hardware device. In other embodiments (for example, embodiments that utilize software-defined networking (SDN)), the control functions and the forwarding functions of network moduleare performed on physically separate devices, such that the control functions manage several different network hardware devices. Computer readable program instructions for performing the inventive methods can typically be downloaded to computerfrom an external computer or external storage device through a network adapter card or network interface included in network module.

1002 WANis any wide area network (for example, the internet) capable of communicating computer data over non-local distances by any technology for communicating computer data, now known or to be developed in the future. In some embodiments, the WAN may be replaced and/or supplemented by local area networks (LANs) designed to communicate data between devices located in a local area, such as a Wi-Fi network. The WAN and/or LANs typically include computer hardware such as copper transmission cables, optical transmission fibers, wireless transmission, routers, firewalls, switches, gateway computers and edge servers.

1003 1001 1001 1003 1001 1001 1015 1001 1002 1003 1003 1003 End user device (EUD)is any computer system that is used and controlled by an end user (for example, a customer of an enterprise that operates computer), and may take any of the forms discussed above in connection with computer. EUDtypically receives helpful and useful data from the operations of computer. For example, in a hypothetical case where computeris designed to provide a recommendation to an end user, this recommendation would typically be communicated from network moduleof computerthrough WANto EUD. In this way, EUDcan display, or otherwise present, the recommendation to an end user. In some embodiments, EUDmay be a client device, such as thin client, heavy client, mainframe computer, desktop computer and so on.

1004 1001 1004 1001 1004 1001 1001 1001 1030 1004 Remote serveris any computer system that serves at least some data and/or functionality to computer. Remote servermay be controlled and used by the same entity that operates computer. Remote serverrepresents the machine(s) that collect and store helpful and useful data for use by other computers, such as computer. For example, in a hypothetical case where computeris designed and programmed to provide a recommendation based on historical data, then this historical data may be provided to computerfrom remote databaseof remote server.

1005 1005 1041 1005 1042 1005 1043 1044 1041 1040 1005 1002 Public cloudis any computer system available for use by multiple entities that provides on-demand availability of computer system resources and/or other computer capabilities, especially data storage (cloud storage) and computing power, without direct active management by the user. Cloud computing typically leverages sharing of resources to achieve coherence and economies of scale. The direct and active management of the computing resources of public cloudis performed by the computer hardware and/or software of cloud orchestration module. The computing resources provided by public cloudare typically implemented by virtual computing environments that run on various computers making up the computers of host physical machine set, which is the universe of physical computers in and/or available to public cloud. The virtual computing environments (VCEs) typically take the form of virtual machines from virtual machine setand/or containers from container set. It is understood that these VCEs may be stored as images and may be transferred among and between the various physical machine hosts, either as images or after instantiation of the VCE. Cloud orchestration modulemanages the transfer and storage of images, deploys new instantiations of VCEs and manages active instantiations of VCE deployments. Gatewayis the collection of computer software, hardware, and firmware that allows public cloudto communicate through WAN.

Some further explanation of virtualized computing environments (VCEs) will now be provided. VCEs can be stored as “images.” A new active instance of the VCE can be instantiated from the image. Two familiar types of VCEs are virtual machines and containers. A container is a VCE that uses operating-system-level virtualization. This refers to an operating system feature in which the kernel allows the existence of multiple isolated user-space instances, called containers. These isolated user-space instances typically behave as real computers from the point of view of programs running in them. A computer program running on an ordinary operating system can utilize all resources of that computer, such as connected devices, files and folders, network shares, CPU power, and quantifiable hardware capabilities. However, programs running inside a container can only use the contents of the container and devices assigned to the container, a feature which is known as containerization.

1006 1005 1006 1002 1005 1006 Private cloudis similar to public cloud, except that the computing resources are only available for use by a single enterprise. While private cloudis depicted as being in communication with WAN, in other embodiments a private cloud may be disconnected from the internet entirely and only accessible through a local/private network. A hybrid cloud is a composition of multiple clouds of different types (for example, private, community or public cloud types), often respectively implemented by different vendors. Each of the multiple clouds remains a separate and discrete entity, but the larger hybrid cloud architecture is bound together by standardized or proprietary technology that enables orchestration, management, and/or data/application portability between the multiple constituent clouds. In this embodiment, public cloudand private cloudare both part of a larger hybrid cloud.

The descriptions of the various embodiments of the present disclosure have been presented for purposes of illustration, but are not intended to be exhaustive or limited to the embodiments disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The terminology used herein was chosen to best explain the principles of the embodiments, the practical application or technical improvement over technologies found in the marketplace, and to enable others of ordinary skill in the art to understand the embodiments disclosed herein.